Apparatus and method of forming and projecting high precision optical images

ABSTRACT

An apparatus for projecting high precision optical images with a selective heating source, advantageously a laser, on a writable, erasable, editable electronic slide and simultaneously or sequentially projecting the images in registration, onto a receiving surface such as a projection screen or photosensitive material, in the former case for the purpose of displaying the projected image and in the latter case for the purpose of creating a hard copy of the projected image.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an apparatus and method of forming andprojecting high precision optical images and more particularly to amethod of forming the images by writing and editing with a selectiveheating source, advantageously a laser, on a writable, erasable,editable electronic slide and simultaneously or sequentially projectingthe images, in registration, onto a receiving surface such as aprojection screen or photosensitive material, in the former case for thepurpose of displaying the projected image and in the latter case for thepurpose of creating a hard copy of the projected image.

2. Discussion of the Prior Art

Prior art relative to this invention relates firstly to methods forcreating the slices or images to be projected and secondly to methodsfor projecting the slides so that certain subimages are in registration.Registration of the subimages is important for a variety of applicationssuch as the creation of color images. The text Display SystemsEngineering, edited by H. R. Luxenberg and R. L. Kuehn (1968) broadlysummarizes the art prior to 1968. More recent art has been reviewed byCarbone (Large Screen Display Technology Survey, Richard M. Carbone, TheMITRE Corporation, Bedford, Mass., November 1982) and Todd (Lee T. Todd,Jr., Projection Display Devices, Society for Information Display,Seminar Lecture Notes, Vol. II, Paper 8.1, May 3, 1985).

Traditionally slices or images for projection have been createdphotographically by exposure of a light sensitive emulsion or by meansof a scribing system in which a sharp point or stylus scratches theinformation into an opaque coating on a glass plate or film. Thephotographic method is not spontaneous and does not permit real-timeupdate with new information or simultaneous writing and viewing. It alsorequires apparatus for film processing as well as writing. The scribingmethod permits real time viewing and updates but erasure of previouslyscribed information is impractical and the scribing rates are relativelyslow.

Projection systems in which the cathodoluminescent target of a cathoderay tube serves as an electronic slide or image source overcome thedisadvantages of the photographic and scribing approaches but arelimited in image brightness and resolution. The projected imagebrightness is limited by saturation of the phosphor output as the CRTelectron beam current is increased, by phosphor burn and faceplatefailure due to overheating by excessive beam currents, and by practicallimits on the physical size of the optics used for image projection.Resolution is limited by the increase in focused beam spot size withincreased beam current, resulting in a brightness-resolution tradeoff,and by the need for high bandwidth refresh circuits to refresh theprojected images at 60 Hz or more in order to eliminate visible flicker.For example, a 4000×4000 picture element image refreshed at 60 Hz wouldrequire a 960 MHz data input. Even if such a high bandwidth data ratewere practical, positioning of an electron beam to the positionalaccuracy required for such a display would require extremely expensivebeam indexing built into the tube or extremely stable, i.e., expensive,analog electronics. Strong magnetic shielding would be required tominimize the effect of terrestrial magnetism and local magnetic fieldvariations on the electron beam position. Large area CRTs with imagediagonals up to about 40 inches have been constructed, but theirresolution is also limited by the aforementioned constraints on datarate and beam positional accuracy. Storage CRTs have been built whichovercome the need for high bandwidth .refresh, but storage CRTs havesignificantly lower lumen output than refreshed CRTs and are thereforeof limited interest for projection systems and the direct view unitsmust be used in rooms with subdued lighting.

The aforementioned constraints on brightness of systems incorporatingCRTs with cathodoluminescent targets are overcome by a class of devicesknown as electronic light valves. In these electronic light valves, thereflection or transmission properties of a physical medium is spatiallyand temporally varied by electronic means. These electronic means mayinclude electronic scanning of an electron or optical beam or gating ofa voltage across the light valve medium by an electrode array. The lightvalve can then be used to control the flow of light from a light sourceto a receiving target. With appropriate optics to image the light valveon the receiving target, the spatial and temporal variations imposed bythe electronic means on the light valve can be faithfully reproduced atthe position of the receiving target. Commercial light valve systemshave been introduced with capabilities to project images withinformation content up to about 2000 TV lines.

A new type of electronic light valve display based on a laser scannedsmectic (LSS) liquid crystal and capable of storing and projectingimages with significantly higher than 2000 TV line information contentwas described by Kahn (Frederic J. Kahn, U.S. Pat. No. 3,796,999, March1974). Even images with lower than 2000 line information content havesignificantly improved definition due to the resolution of the LSS lightvalves. More recent developments in LSS technology have been reviewed byDewey (A. G. Dewey, Laser-Addressed Liquid Crystal Displays, Opticalengineering, May-June 1984, Vol. 23, pp. 230-240).

LSS light valves consist of a thin layer of smectic liquid crystalsandwiched between two substrates. The image is written thermally byscanning a focused laser beam across the light valve. The entire imagecan be erased in a small fraction of a second by applying a voltageacross the smectic layer. The writing beam can be transformed into anerasing beam for local editing of the written image by applying asomewhat lower voltage than required for erase of the entire image. Whensuch a voltage is applied only those regions which are reheated by thelaser beam will be erased. Advantages of these thermal smectic lightvalves in addition to the high resolution, erase, and local editingfeatures are (1) the image is stored in the liquid crystal untilelectrically erased, thus no image refresh is required, (2) the opticalproperties of the image are relatively wavelength independent; thusthese light valves can be used to control light from the near uv throughthe ir and any part of the spectrum in between, (3) there is minimalabsorption of light by the liquid crystal and associated opticalelements, thus this light valve can be used to control very highintensity light sources with high optical efficiency, (4) laserabsorbers can be constructed to match a wide range of laser wavelengthsthereby enabling use of a wide variety of writing lasers includingsemiconductor lasers which are relatively economical, compact, andreliable.

Despite the significant advantages cited above, commercial applicationof the LSS light valves has been limited by the complex and expensivescanning mechanisms required for creating very high information contentimages, the inability to scan precisely in a repeatable fashion, theunavailability of a method practical for creating a high resolution fullcolor image without using multiple scanners, the unavailability of ascan system for high resolution full color images with random access aswell as raster scan capabilities, the inability to display bright fullcolor images with moderate power light sources, and the inability toimplement a practical on-screen cursor. Thus a display and imagingsystem capable of creating precision, very high information content,full color, random scan images with a relatively simple writing systemand a relatively low power projection source is desired. An additionaldesirable feature is a cursor. Furthermore the same precision imagewriting and projection capabilities desired for creation of full colorimages are required for producing and registering images onphotosensitive hard copy materials.

SUMMARY OF THE INVENTION

This invention relates to a method of forming and projecting highprecision optical images and more particularly, to a method of formingthe images by writing and editing with a selective heating source,advantageously a laser, on a writable, erasable, editable electronicslide and simultaneously or sequentially projecting the images, inregistration, onto a receiving surface such as a projection screen orphotosensitive material. The present apparatus and method provides forefficient use of the projection light source and excellent spatialfidelity of the projected image relative to the original image, theoriginal image being electronically entered into the image forming andprojection system.

The preferred method and apparatus for forming the image provides forprecision scanning of a focused laser beam across a light sensitivelayer which stores a pattern of information determined by a thetrajectory of the laser beam. The position of the beam is varied with asingle scan system. This position of the beam on the entire lightsensitive layer is controlled by a servo system which corrects the laserbeam trajectory by comparing the desired position signal with actualposition to derive an error signal.

The series of trajectories so created are stored in a liquid crystalcell which is patterned into one or more subcells each one of which isindependently writable, erasable, and editable by means of the scannedlaser beam and appropriate electrical control voltages.

Different cells which are operable in either transmission or reflectioncan be fabricated. A reflection cell structure is preferred for colordisplay and hard copy printing applications because reflective cells canwithstand the required intense illumination levels.

The method for creating a color projection display consists of assigninga different primary projection color, e.g., red, green, blue for anadditive color system with broad spectral coverage, to each of severalsubcells, and where desired, to use an additional subcell for anindependent cursor or overlay. These subcells are coprojected inregistration to achieve a full color image with cursor or overlay. Oneor more detectors are provided at the edge of the receiving surface forthe projected image in order to facilitate satisfactory registration ofthe projected image with that surface.

The preferred method for projecting the full color images together withan overlay plane which can be used, for example, for implementing acursor consists of taking the output from a single lamp and splitting itinto two white channels. One white channel is subdivided into threecolor beams (red, green, and blue). These three color beams togetherwith the remaining white beam are preferably imaged by means of a singlerelay condenser onto the liquid crystal cell so that each beamilluminates primarily only one subcell. The relay condenser forms animage of the lamp on the aperture of each of four projection lenses, onefor each beam. The projection lenses are positioned so as to project thesubimages in registration onto a single receiving surface so as toresult in a full-color image with cursor/overlay on that surface. Thisprojection method is highly efficient in collecting light andtransferring it to the receiving surface which for display applicationscan be a rear projection screen.

Electronic means are provided to correct for residual distortion andpositional differences in the images written on the subcells so as toprovide image registration to within a fraction of the minimum linewidthwhich can be written and projected. The method for distortion correctioninvolves use of a look up table with table entries keyed to sections ofthe image.

It is a general object of the present invention to provide an improvedapparatus and method for forming and projecting optical images.

It is another object of the present invention to provide an apparatusfor forming and projecting optical images which are formedelectronically on light valves in general and smectic liquid crystallight valves in particular

It is a further object of the present invention to provide an apparatusand method for forming and projection a plurality of separate images inregistration.

It is another object of the present invention to provide an apparatusand method for forming images on a liquid crystal cell and forprojecting said images in registration by reflection from the cell.

The foregoing and other objects of the invention are achieved by asystem in which stored images are projected by reflection from an imagesource such as a liquid crystal.

The foregoing and other objects of the invention will be more clearlyunderstood from the following description when read in conjunction withthe accompanying drawings of which:

FIG. 1 is a schematic view showing primarily a reflection projectionsystem in accordance with the invention.

FIG. 2 shows the positioning of the projection lens.

FIG. 3 is a schematic diagram showing an electronic imaging system inaccordance with the invention.

FIG. 4 is a schematic diagram showing the combined imaging andprojection system.

DETAILED DESCRIPTION OF THE DRAWING

The present invention relates to a method for electronically creatinghigh precision optical images and, more particularly, to a method forcreating images which have precisely controlled geometries and which canbe uniformly registered with each other by coprojection onto a receivingsurface such as a projection screen or photosensitive material. Aspecific embodiment of this invention is a high information content,large area display apparatus for full-color images. Another is anapparatus for printing full-color hard copy.

FIG. 1 shows a projection system 100 employed in the present invention.A source of radiation energy or light 101, illustratively a 1000 wattXenon arc lamp, emits light which is collected by an optical system 102and directed onto reflective object 104 in such manner that each beamilluminates primarily one particular area or section of object 104. Suchan illumination system designed for transmission projection of multipleslide images is described on pp. 197-199 of Luxenberg and Kuehn. In thepresent invention the light reflected from each area illuminates theaperture of one particular lens of lens array 105, illustrativelyconsisting of multielement lenses with achromatized designs. Lens array105 images the reflective object 104, illustratively a pattern withspatially varying reflectivity, on the receiving surface 106,illustratively a rear projection screen, in such manner that thereceived images of each section of object 105 are precisely registeredwith each other on surface 106. The illumination axes of the lenses inarray 105 are slightly tilted relative to each other so that they willconverge at the center of surface 106. The lens positions are determinedby drawing the rays connecting the extrema of the subimages and theextrema of the receiving surface and locating the lenses at theintersection of the rays. These locations provide for coregistration ofthe images on the receiving surface as shown in FIG. 2. Image positionsensor 107, located on the receiving surface or at an opticallyequivalent position, is used to detect temporal shifts in position ofthe received image. Illustratively a registration pattern may beprojected on sensor 107, and the signal from sensor 107 processed byprocessor 108 to determine the position of that registration pattern andhence to determine the position of the image which has a known spatialrelationship to the registration pattern. In a preferred embodiment,keystone distortion can be avoided by making the planes of object 104,array 105 and surface 106 parallel to each other. Alternatively,keystoning can be electronically corrected by predistorting the image onreflective object 104; and resulting focus shifts, when 104, 105, and106 are not coplanar, can be corrected by satisfying the Scheimpflugcondition.

Distortions in the projected image contributed by individual lenses inarray 105 and by residual misalignments and imperfections in theprojection system, can be similarly corrected by predistorting the imagefound on reflective object 104. For this purpose processor 108 includeselectronic means for correcting distortions of the projected image,illustratively by means of a look-up table in which corrections due tothe computed distortion of the writing system 300, FIG. 3, the computeddistortion of the projection lenses, and the residual distortiondetermined experimentally after the computed distortions have beencorrected for, are treated additively to compute the entries in thelook-up table. Illustratively, the size of the look-up table and hencethe memory required to store it may be minimized be entering values onlyfor selected points or the projected image and using interpolationalgorithms to determine the values at intermediate points. Processor 108also includes electronic means for decoding the position shiftstransmitted by image position sensor 107 which is physically linked toreceiving surface 106 and for correcting the position of the reflectiveimages on 104 in such manner that they will project with the correctpositions relative to receiving surface 106 and sensor 107.Illustratively, sensor 107 may consist of one or more patterned maskspositioned in front of one or more photodetectors. Processor 108includes controller 309 and servo 308 shown in FIG. 3.

The reflective object 104 described above may be a static image, e.g., apattern of aluminum or chrome on a transparent substrate such as glass.Such an object due to its minimal light absorption in both thereflecting and transmitting regions will be suitable for projection ofvery intense illumination levels onto the receiving surface. Thereflectivity of the metallic reflecting regions may be enhanced by meansof well known thin film dielectric coatings. Similarly the transmittanceof the nonreflecting regions and hence the resultant contrast of themask may also be enhanced by thin film dielectric coatings.

The reflective object may be an image which can be written and erased byelectronic means, i.e., an electronic light valve. Preferably, thereflective object may be a laser scanned smectic (LSS) liquid crystallight valve. By patterning the conducting electrodes of such a device itis possible to selectively apply higher electric fields to one or moreindependently selected sections, e.g., 104a, 104b, 104c or 104d, than tothe remaining unselected sections of the same device and thereby toindependently erase the individual selected sections or to editlaser-selected portions of the individual selected sections.

Use of a single condenser 109 in the directing optical system 103 toilluminate two or more of the projection lenses in array 105 isadvantageous in enabling faster (larger aperture) projection lenses tobe employed and higher image-to-object magnification ratios to beachieved than would be the case if each projection lens had its ownilluminating condenser. Without a single condenser it would be necessaryto use projection lenses with very small apertures, which would resultin unacceptably low image brightness, or impractically large off-normalangles of incidence on object 104. Therefore a multiple imagingreflective system is impractical. The projection lenses 110 in array 105are preferably multielement lenses in which the optical power isconcentrated primarily in the inner elements and achromatization isconcentrated primarily in the outer elements in order to provideindividual lenses with lengths from front-to-rear surface less than onehalf their total focal length, thereby providing a compact projectionsystem design with a relatively small off-normal projection angle, highresolution and low projection lens distortion. The preferred projectionsystem includes a single condenser 109 in the directing optical system103, a collecting optical system 102 which splits the light into 4 beamswith predominately red, green, blue, and white wavelengths respectively,a reflective object 104 with four subobjects arranged with Manhattangeometry as in FIG. 1, and a rectangular array of 4 lenses 105 toproject the subimages in registration onto receiving surface 107. Thecoregistered red, green, and blue projected images provide a full colorprojected image on surfaced 107 while coprojection of the white imageenables realization of an independent cursor or overlay plane superposedon that full color image. Furthermore the derivation of the red, green,and blue beams from a single white beam by use of dichroic filters incollecting optical system 102 results in a relatively bright projectedimage on surface 107. Alternatively it may be desirable to add color orneutral density filters to modify the color or intensity of the whiteoverlay channel or to add a blue filter to the white channel and use itto enhance the brightness of the blue part of the full color images.

In one embodiment image position sensor 107 may include a patterned maskand a photodetector positioned such that a portion of the imageprojected on receiving surface 106 is in focus on the patterned mask andis transmitted through that mask before reaching the photodetector. Ifthe mask pattern includes at least two regions with differingtransmissions and a sharp (edge) boundary between them, stepwise orcontinuous movement across that boundary of a projected image alsocontaining at least one edge will result in a change in the output ofthe photodetector enabling unique determination of the writing systemcoordinates positioning the projected edge at the position of the maskedge. It may be advantageous to use more than one image position sensor107, for example, to determine rotational as well as translationalshifts in image position and to correct for the same by means ofprocessor 108.

In another example of a projection system embodying the invention, lensarray 105 includes only a single lens and only a single image at a timeis projected onto receiving surface 107. Image position sensor 107 incombination with processor 108 can serve to maintain positionalregistration between the projected image and the receiving surface.

The combination of image position sensor 107 and processor 108 will alsobe useful for maintaining image-to-receiving surface 106 registration inprojection systems with transmissive objects and in which the lightsource 101 and projection lenses 105 are located on opposite sides ofthe object 104.

FIG. 3 shows a writing system employed in the present invention. A beamof light from writing source 301 is focused and scanned across object305 by scanning system 302. Position sensor 307 measures changes inposition of the scanning mirrors, illustratively mirror 303, in scanningsystem 302 and provides an output signal containing the information onthese changes to servo 308. Servo 308 provides the electronic drivesignal for scanning system 302 in such a manner as to result in minimaldifferences between the desired mirror positions provided by controller309 and the actual mirror positions determined by mirror position sensor307 in combination with servo 308. A beam position sensor 306 is locatedat the surface of object 305 or at an optically equivalent position.Object 305 receives the focused spatially scanned laser beam and sensor306 provides an absolute reference relating the position of the laserbeam on object 305 and sensor 306 to the scanning mirror positions.Controller 309 electronically corrects the desired mirror positionsignal to account for temporal position shifts sensed by beam positionsensor 306. Illustratively, sensor 306 may consist of one or morepatterned mask and photodetector pairs analogous to sensor 107 describedabove. In one embodiment, patterning of the masks to include at leastone edge or boundary separating two areas of different transmission willenable detection of the writing beam position as it moves across thatedge. Thus, beam position sensor 306 may illustratively be similar instructure and operation to image position sensor 107 except that it isthe scanned laser beam itself which is detected rather than an edgecontained in a projected image.

Writing source 301 may illustratively include a semiconductor laserwhich emits light with a wavelength of about 800 nm, prisms and lensesto circularize, enlarge, and collimate the laser beam, and an electricalcircuit to vary the intensity of the beam in a timewise fashion.Scanning system 302, in addition to including at least one mirror 303 todeflect the laser beam, may illustratively include a galvanometer 304 todrive the laser beam deflecting mirror and a scan lens, illustrativelyan f-theta lens, to convert angular deflections of the laser beam intospatial deflections of a focused laser beam spot along the surface ofobject 305. Mirror position sensor 307 may include light sources andgratings 310 and detectors with grating reticles 311 enablingdetermination of the positions and the directions of movement of eachscanning mirror. A particular embodiment of mirror position sensor 307is described in companion application entitled Apparatus for DetectingPosition.

Controller 309 illustratively may include a graphics processor withmeans to receive a variety of graphics inputs from external electronicimage sources, a vector generator to provide the desired scan positioninformation signal for the servo 308, control signals for modulating thewrite source 301, and electrical signals for erasing and editing of thevarious sections of object 305 when that object is an electronic lightvalve.

Object 305 may be one of many different devices. For example, it may bea previously patterned reflective or transmissive object to be scannedby the laser beam, illustratively for the purpose of inputting datarelated to the patterns recorded on said object into an informationprocessing or storage system. Variations in intensity of the scannedlaser beam after reflection or transmission from the object may besensed by one or more appropriately positioned photodetectors. Object305 may be a recording material sensitive to the wavelength of thescanned laser beam, illustratively infrared sensitive paper or film.Object 305 may be an electronic light valve illustratively including aphotoconductive layer sensitive to the wavelength of the scanned laserbeam. Object 305 may be a transmissive mode LSS light valve,illustratively including a dye absorbing at the scanned laser wavelengthand mixed into the liquid crystal for the purpose of absorbing heattransported by the scanned laser beam directly into the liquid crystallayer.

Object 305 may be a reflective mode LSS light valve. Preferably theobject 305 consists of 4 subimages arranged in a Manhattan geometry on asingle object as shown in FIG. 3 so as to enable scanning of the entireimage with a single scanner and to minimize variations in the relativepositions of these subimages dues to mechanical and thermaldisturbances, thereby facilitating precise coregistration of thecoprojected images.

FIG. 4 shows a combined writing and projection system consisting of aprojection system 406 and a writing system 407 which include a commonobject 403, a beam position sensor 404 physically linked to object 403,a receiving surface 401, an image edge detector 402 physically linked toreceiving surface 401, and a controller 405. Controller 405 receives theposition signals from sensors 402 and 404 and corrects the position ofthe object image on object 403 so as to result in accurate registrationof the projected image with respect to receiving surface 401 in keepingwith the preceding discussions of projection system 100 and writingsystem 300.

Thus there is provided a system for forming and projecting anddisplaying or recording high precision optical images.

What is claimed is:
 1. A projection apparatus includinga light source,an image object plane containing at least two spaced reflecting images,optical means including a single condenser lens disposed to receivelight from said source and form at least two beams and directing one ofsaid beams on each of said reflecting images, at least two spacedmultielement projection lenses in which the power is concentratedprimarily in the inner elements and achromatization is concentratedprimarily in the outer elements to provide lenses with front to rearsurface lengths less than half the focal length to provide a compactdesign with relatively small off-axis angle, high resolution and lowdistortion, said projection lenses positioned to receive light reflectedby said images on to a receiving plane so that the images are incoregistration.
 2. A projection apparatus as in claim 1 in which thespaced reflecting images are disposed on a single object.
 3. Aprojection apparatus as in claim 1 in which the image object planecomprises an electronic light valve.
 4. A projection apparatus as inclaim 1 in which the image object plane comprises a smectic liquidcrystal.
 5. A projection apparatus includinga light source, an imageobject plane containing at least three spaced reflecting images, opticalmeans including a single condenser lens disposed to receive light fromsaid source and form at least three beams with light of differentwavelengths and directing said beams, one on each of said reflectingimages, at least three spaced multielement projection lenses in whichthe power is concentrated primarily in the inner elements andachromatization is concentrated primarily in the outer elements toprovide lenses with front to rear surface lengths less than half thefocal length to provide a compact design with relatively small off-axisangle, high resolution and low distortion, said projection lensespositioned to receive light reflected by said images and direct thelight from said images onto a receiving plane so that the images are incoregistration.
 6. A projection apparatus as in claim 5 in which saidimage object plane contains four images, said optical means forms fourbeams and four projection lenses direct the light onto said receivingplane.
 7. An apparatus for projecting an image on a projection planeincludingan image object plane comprising an electronic light valve,means forming at least one image on said electronic light valve, a lightsource, optical means for receiving light from said light source andforming at least one beam and directing said beam to said electroniclight valve image, at least one projecting lens positioned to receivelight from said light valve image and direct the light to saidprojection plane, means at said projection plane for sensing theposition of the image on the projection plane and means for controllingthe image forming means for positioning the image on said electroniclight valve responsive to the position sensed by the position sensingmeans.
 8. A projection apparatus as in claim 7 in which said opticalmeans includes a single condensor lens to illuminate the projectionlenses.
 9. A projection apparatus as in claim 7 in which said projectorlenses are multielement lenses in which the power is concentratedprimarily in the inner elements and achromatization is concentratedprimarily in the outer elements to provide lenses with front to rearsurface lengths less than half the focal length to provide a compactdesign with relatively small off-axis angle, high resolution and lowdistortion.
 10. A projection apparatus as in claim 8 in which saidprojector lenses are multielement lenses in which the power isconcentrated primarily in the inner elements and achromatization isconcentrated primarily in the outer elements to provide lenses withfront to rear surface lengths less than half the focal length to providea compact design with relatively small off-axis angle, high resolutionand low distortion.
 11. An apparatus for projecting an image on aprojection plane includingan image object plane comprising an electroniclight valve, means forming at least a plurality of images on saidelectronic light valve, a light source, optical means for receivinglight from said light source and forming a plurality of beams anddirecting said beams to the images on said electronic light valve, aplurality of projecting lenses positioned to receive light from saidlight valve image and direct the light from each image in registrationon said projection plane, means at said projection plane for sensing theposition of each image on the projection plane and means for controllingthe image forming means for positioning each image on said electroniclight valve responsive to the position sensed by the position sensingmeans to assure positioning and registration.
 12. A projection apparatusas in claim 11 in which said optical means includes a single condensorlens to illuminate the projection lenses.
 13. A projection apparatus asin claim 12 in which said projector lenses are multielement lenses inwhich the power is concentrated primarily in the inner elements andachromatization is concentrated primarily in the outer elements toprovide lenses with front to rear surface lengths less than half thefocal length to provide a compact design with relatively small off-axisangle, high resolution and low distortion.
 14. Apparatus as in claim 11wherein said images are reflective images.
 15. Apparatus as in claim 11wherein said beams are of light having different wavelengths.
 16. Anapparatus for projecting an image on a projection plane includinganimage object plane comprising an electronic light valve, means formingat least one image on said electronic light valve, means for controllingthe image forming means so that it records a distorted image which uponprojection has the fidelity of the intended image, a light source,optical means for receiving light from said light source and forming atleast one beam and directing said beam to said electronic light valveimage, at least one projecting lens positioned to receive light fromsaid light valve image and direct the light to said projection plane toform an image on said plane.
 17. Apparatus as in claim 16 in which saidimage is a reflective image.
 18. An apparatus for projecting an image ona projection plane includingan image object plane comprising anelectronic light, valve, means forming at least a plurality of images onsaid electronic light valve, means for controlling the image formingmeans so that it records a distorted image which upon projection has thefidelity of the intended image, a light source, optical means forreceiving light from said light source and forming a plurality of beamsand directing said beams to the images on said electronic light valve, aplurality of projecting lenses positioned to receive light from saidlight valve image and direct the light from each image in registrationon said projection plane to form an image on said plane.
 19. Aprojection apparatus as in claim 18 wherein said images are reflectiveimages.
 20. A projection apparatus as in claim 18 wherein said beams areof light having different wavelengths.
 21. A projection apparatus as inclaim 20 in which said optical means includes a single condensor lens toilluminate the projection lenses.
 22. A projection apparatus as in claim21 in which said projector lenses are multielement lenses in which thepower is concentrated primarily in the inner elements andachromatization is concentrated primarily in the outer elements toprovide lenses with front to rear surface lengths less than half thefocal length to provide a compact design with relatively small off-axisangle, high resolution and low distortion.
 23. An apparatus forprojecting an image on a projection plane includingan image object planecomprising an electronic light valve, means forming a light beam, meansfor scanning the electronic light valve with the light beam to form atleast one image on said electronic light valve, means for controllingthe light beam so that it records a distorted image which uponprojection compensates for aberrations in the optics and to project theintended image on an image plane with high fidelity, a light source,optical means for receiving light from said light source and forming atleast one beam and directing said beam to said electronic light valveimage, and at least one projecting lens positioned to receive light fromsaid light valve image and direct the light to said projection plane toform an image on said plane.
 24. An apparatus as in claim 23includingmeans at the image plane for sensing the position of the image,and means for controlling the position of the light beam responsive tothe position sensed by the positioning sensing means.
 25. An apparatusas in claim 23 includingmeans for scanning the light beam to formmultiple images on said electronic light valve, and including multipleprojection lenses to project said images in registration on an imagereceiving surface.
 26. An apparatus as in claim 25 in which theelectronic light valve operates in the reflective mode whereby imagesare reflected and projected.
 27. An apparatus as in claim 26 whichincludes a single condenser to illuminate the image and projection lens.